Stereo laser endoscope

ABSTRACT

A converging laser operating beam is directed to a target site by a gimbal mounted mirror having a pair of apertures through which the work site is viewed simultaneously by a stereo microscope. To locate the focal point of the operating beam, diverging light from a marker light point source is reflected back through the microscope by reflective means mounted over the apertures on the mirror. The marker light provides a virtual image which appears to the viewer as a spot coincident with the focal point of the operating beam. A joy stick is mechanically linked to the mirror so that the beam, along with the marker light spot, may be steered to any desired location within a few degrees of the central optical axis of the microscope. Means are also provided for using a conventional stereo microscope&#39;&#39;s selfcontained light source for the marker light source.

United States Patent Bredemeier 1 Mar. 12, 1974 i 1 STEREO LASERENDOSCOPE Primary Examiner-Lawrence W. Trapp [76] Inventor: Herbert C.Bredemeler, 5 Bridle gi Agent or Firm-Lane Anken Dunner &

Path, Sherborn, Mass. 01770 [22] Filed: Mar. 24, 1972 57] ABSTRACT [21]A l, N 237,790 A converging laser operating beam is directed to a targetsite by a gimbal mounted mirror having a pair of apertures through whichthe work site is viewed simul- [52] US. Cl. 128/302236,11b21/7?;g55taneously by a Stereo microscopa To locate the focal [51] Int. Cl 6. 35035 point of the operating beam, diverging light from a [58] meld ofSearch marker light point source is reflected back through the 350/microscope by reflective means mounted over the apf d ertures on themirror. The marker light provides a vir- [56] Re erences tual imagewhich appears to the viewer as a spot coin- UNITED STATES PATENTS cidentwith the focal point of the operating beam. A 3,703,176 11/1972Vassiliadis et a1. 128/395 joy stick is mechanically linked to themirror so that 3,424,5l8 1/1969 Sato et al 350/35 X the beam, along withthe marker light spot, may be 35421007 Roberts et 123/395 steered to anydesired location within a few degrees of 5 et a1 the central opticalaxis of the microscope. Means are yer.... 1 3,533,707 10/1970 Weiss350/91 also pmv'ded for 3 convennonal Stereo mlcm scopes self-containedlight source for the marker light source.

35 Claims, 12 Drawing Figures PAIENIEDIAR 12 1914 3.796220 SHEET 1 OF 5FIG].

MARKER LIGHT SOURCE PATENIEDIARIZBN $796220 SHEET h [if 5 PAIENTEU IIARI 2 i974 SHEEF 5 OF 5 Fla/I.

STEREO LASER ENDOSCOPE BACKGROUND OF THE INVENTION The invention relatesgenerally to the field of laser microsurgery, and more particularly tooptical apparatus for directing a focused laser beam to a target sitewhile providing a microscopic view of the work area.

In the past, highly focused laser beams have been used clinically, forexample, for treatment of the eye by photo-coagulation. As a precisecutting tool, the laser is finding many new applications in the field ofmedical research. Because laser light can be highly focused, the laserbeam is capable of performing surgery at microscopic dimensions inareas, such as the inner ear, which were formerly inaccessible toconventional surgical instruments. There is, therefore, a growing demandfor laser equipment with which the surgeon can safely and efficientlyutilize the laser.

ln former laser instrumentation, many problems have been encountered inattempting to meet the surgions need for precise location and control ofthe focused laser beam. If the focused spot size is on the order of lOOmicrons, of course, the work site must be viewed with a microscope tocorrectly position the spot and follow the process of the surgery. Ithas been found that the site can be viewed directly through a beamsplitter arranged to reflect a portion of the laser energy to the targetsite. Besides needlessly obstructing the surgions view and subtractingfrom the deliverable beam power, prior systems employing this principlehave tended to detract from the desired maneuverability of the focusedlaser beam. Since the beam splitter and microscope were rigidlyconnected to each other, and in some manner to the source of laserenergy, moving the laser spot to a specific neighboring locationrequired moving the microscope as well as the beam splitter, and wastherefore an extremely delicate task whose difficulty was whollydisproportionate to the degree of mancuverability normally required. Inall of the known prior systems a visible marker light was used toprelocate the position of the laser spot before applying maximum energyto the target site. The marker systems all required at least oneauxiliary light beam to be focused on the work site coincidentally withthe normal focal point of the laser beam. Many employed complicatedshutter systems to temporarily introduce a marker light coaxially withthe laser beam path. When moving the spot to a new location, the markersystem usually had to be moved,too. In short, the complex prior artsystems, because of their bulk and lack of flexibility, were unsuitablefor delicate operations requiring confident, precisely controlledmanipulation of the laser spot.

SUMMARY OF THE INVENTION Accordingly, one of the objects of theinvention is to provide improved means for viewing the work site alongthe optical axis of the laser operating beam. Another object of theinvention is to provide a binocular viewing system which does notinterfere with the operating beam. A further object of the invention isto provide means for changing the orientation of the laser beam withrespect to the viewing system in order to select a neighboring targetsite within the stationary field of view. Still another object of theinvention is to provide a continuous marking system using'a virtualimage which follows the location of the focal point of the laser beamand interferes minimally with the surgeons view.

The applicant has discovered that these and other objects of theinvention are accomplished by directing a converging laser operatingbeam to a work site by a gimbal mounted mirror having a pair ofapertures through which the work area is viewed simultaneously with aconventional stereo operating microscope. The two apertures are centeredrespectively on the converging stereo axes of the microscope so that themi croscopes normal field of view is unobstructed. The laser beam isreflected downwardly by the mirror from a point between the twoapertures along the central optical axis (the bisector of the stereoaxes) of the microscope towards the work area.

A marker system is provided to indicate the location of the laser beam.A marker light point source is located facing the other side of themirror opposite the impinging laser beam. A converging lens system isinterposed between the marker light source and the mirror to make thelight source appear as if it were located at the working distance of themicroscope. Means are disposed in each of the two apertures in themirror to reflect the marker light into the microscope objective fromthe same plane as that from which the impinging laser beam is reflectedto the target site. With proper adjustment, the virtual image of themarker light point source therefore appears to the surgeon to be locatedcoincidentally with the focal point of the laser beam. In oneembodiment, the reflecting means in the mirror apertures are formed byplacing beam splitters over the apertures on the same side from whichthe laser beam is reflected. In another embodiment, a fully reflectivesurface covers a small portion of each aperture and lies in the sameplane as the laser beam reflecting surface between the apertures.

To provide flexibility in locating the focal point of the laser beamwith respect to the subject, without actually moving the subject or thestereo microscope, means are provided for changing the orientation ofthe exiting laser beam, and concomitantly the orientation of the markerimage, within a few degrees of the central optical axis of thestationary microscope in any direction. The apertured mirror is mountedin a gimbal assembly having two orthogonal axes of rotation- A singlecontrol handle, which operates like an airplane joy stick," ismechanically linked to the gimbal assembly to provide sensitive, controlrotation about either of the gimbal axes, separately or simultaneously.The resulting movement of the focal point of the laser beam, and thevirtual image of the marker source, is proportional to and in the samesense as the movement of the joy stick.

In another embodiment, the separate marker light source is replaced bythe internal light source of a conventional stereo microscope. Toaccomplish this, the marker point source is formed by one end of a fiberoptic light guide whose other end is located adjacent to the mirror forreceiving light generated internally by the microscope. At the sametime, the microscopes light source also serves its intended function ofilluminating the operating site.

While the laser beam directing and viewing system is applicable toexternal surgery, the system finds its greatest use and advantage inendoscopic operations, for which the system is adapted by enclosing theoptical path to the work site with an appropriate tubular or conicalsheath permitting insertion of the instrument.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an embodimentof the stereo laser endoscope according to the invention, illustratingthe relative locations of the laser beam, marker light source, gimbalmounted mirror, and joy stick control.

FIG. 2 is a sectional view taken along lines 22 of FIG. 1 illustratingin particular the gimbal assembly for the mirror.

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2 illustratingthe optical system in more detail.

FIG. 4 is a sectional view similar to that in FIG. 3 illustrating analternate embodiment of the marker systern.

FIG. 5 is a plan view of an alternative embodiment of the mirrorassembly illustrated in FIG. 2.

FIG. 6 is a cross-sectional view taken along lines 66 of FIG. 5.

FIG. 7 is a plan view with portions broken away illustrating anembodiment of the mechanical linkage between the joy stick and themirror gimbal assembly of FIG. 2.

FIG. 8 is a sectional view taken along lines 8-8 of FIG. 7 illustratingin particular the mounting arrangement for the joy stick.

FIG. 9 is a sectional view along lines 9-9 of FIG. 8 showing inparticular the cams and crank arms of the mechanical linkage for movingthe gimbal assembly.

FIG. 10 is a sectional view similar to that of FIG. 4 illustrating themarker light system in more detail. In this view the laser beam andmarker light systems are reversed and the entire structure is rotated 90compared to FIG. 4.

FIG. 11 is a sectional view of the light guide receiving end adjustmentassembly taken along lines 1111 of F [G 10.

FIG. 12 is an end view of the light guide emitting and alignmentassembly taken along lines 12-12 of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional binocular orstereo operating microscope 10 is shown in FIGS. 1, 2 and 3 with anendoscopic laser accessory 11 enabling an unhindered view of a work site12 while laser energy is applied thereto at a controlled locationindicated by a marker system, explained in detail below. As shown inFIG. 2, the microscope 10 has a pair of separate optical systems withrespective eye pieces 13 and 14 at one end and a common objective lens15 at the other end. Because of the separate optical systems, themicroscope 10 has two optical axies, referred to hereinafter as stereoaxes a and b. The stereo axes a and b converge from the objective lens15 of the microscope 10 toward the focal plane of the microscope at thework site 12. Since the object under observation is viewed from twodifferent angles, as in normal sight, the stereo microscope 10 providesdepth perception, which, of course, is unattainable with a monocularmicroscope. For this reason, the stereo microscope is highly preferredin delicate surgery.

An apertured mirror assembly 16 is arranged obliquely beneath theobjective lens 15 on the microscope's central optical axis c, which isdefined at the bisector ofthe converging stereo axes a and b. The mirrorassembly 16 comprises a rectangular plate 18 having a pair of spacedapertures through which the respective stereo axes a and b pass. Thecentral portion of the side of the plate 18, visible in FIG. 2, iscovered with a fully reflective substance, preferably gold forreflecting infrared energy. The apertures are covered respectively withsemitransparent beam splitters 20 and 22, made of fused silica, forexample, secured to the plate 18.

As shown in FIGS. 1 and 3, the mirror assembly 16 is mounted in ahousing 24 having an opening 26 on one side through which a laser beam27 is introduced perpendicularly to the central axis 0 of the microscope10. A suitable beam of infrared energy, highly absorbable by biologicaltissues, is produced by a C0 gas laser (not shown). The opening 26 canbe directly aligned with the laser source, or the beam can be conveyedto the opening by reflective means (not shown). A converging lens 28 isaligned between the mirror assembly 16 and the opening 26. The mirrorassembly 16 is arranged such that the laser beam 27, after passingthrough the lens 28, is deflected from the reflective central portion ofthe plate 18 downwardly along the microscopes central axis 0 towards thework site 12. The lens 28 is chosen such that the laser beam 27 isfocused to a point lying in the focal plane of the microscope 10, i.e.,at the working distance of the microscope.

For endoscopic surgery, a conical sheath 30 (FIG. 1) may be attached atits larger end to the underside of housing 25 in alignment with thecentral axis 0. The sheath 30 encloses the stereo axes a and h and theconverging laser beam 27 and permits insertion of the instrument intorecessed portions of the subject.

As shown in FIG. 1 and 3, a marker system is provided to indicate theprecise location of the focal point of the laser beam 27. The markersystem is especially necessary when using a C0 laser beam since theinfra red, focused spot, although intense, is invisible to the humaneye. When a visible laser beam is employed as the operating beam 27, themarker system can be used to predict the point of impact of the beambefore the beam is applied. Light from a marker light source 32, whichin its simplest form would be a box with an incandescent bulb, isintroduced through housing 24 by means of an extremely thin (e.g. onestrand) fiber optic light guide 34. One end of the light guide 34 isposi tioned to receive light from the marker source 32. The light guideemitting end 36 is adjustably fixed in housing 24 and extends inwardlydirectly opposite the opening 26 axially aligned with the incoming laserbeam 27. The emitting end 36 forms a point source producing di verginglight rays which are incident on the side of the mirror plate 18 facingthe microscope 10. A converging lens 38 is mounted between the lightemitting end 36 and the mirror assembly 16. A portion of the markerlight incident on the mirror assembly 16 falls within the apertures andis reflected by the inner sides of the beam splitter 20 and 22 (FIG. 2),upwardly into the microscope objective 15 along the stereo axes a and b.The lens is chosen such that the marker light reflectedto the microscope10 is correctly divergent to produce a virtual image of the point sourceformed by the light guide emitting end 36 coincident with the focalpoint of the laser beam. In effect, the lens 38 makes the end 36 appearas if it were at the same distance from the assembly 16 as the targetsite 12. The surgeon viewing the site 12 through the microscope 10 willsee a spot of light which appears to be coincident with the invisiblefocal point of the laser beam, while the actual source of the markerspot is the light guide emitting end 36. To insure coincidence of thelaser focal point and the marker spot as viewed through the microscope10, it is important that the marker light and laser beam 27 be reflectedin opposite directions from approximately the same plane in the mirrorassembly 16. Coplanar reflections are provided by the embodiment ofFIGS. l3 because the marker light is reflected from the inner surface ofthe beam splitter 20, 22 covering each aperture. The inner surface ofeach beam splitter is substantially coplanar with the central reflectivesurface of the plate 18 from which the laser beam is reflected.

In an alternate embodiment 16 of the mirror assembly 16, in FIGS. 5 and6, the beam splitters 20 and 22 are replaced by a ring 40 having atrapezoidal crosssection. The larger flat side of the ring 40 is fullyreflective and is cemented to the laser beam reflecting side of themirror plate 18. The ring 40 is centered between the apertures and has adiameter such that opposite portions of the ring 40 cross over therespective apertures. A portion of the marker light shining on theopposite side of the mirror assembly 16' as viewed in FIG. 5, isincident on the fully reflective surface of the ring portiontransversing each aperture and is reflected back towards the microscope10. Only a small percentage of the area of each aperture is obstructedby the ring 40. Therefore, a larger portion of light is transmitteddirectly through the aperture from the operating site to the microscopethan that which is usually obtained with beam splitters 20 and 22 (FIG.2). Of course, the marker light source 32 must be of sufficientintensity so that the amount of light reflected by the ring 40 to themicroscope 14 is sufficient to produce a visible marker spot image. Thetrapezoidal configuration for the ring cross-section is chosen to reducethe area obscured by the ring in each aperture as viewed from themicroscope 10. The portions of the ring 40 which do not lay over theapertures are unnecessary optically and are used merely to support theportions ofthe ring 40 exposed in the apertures. The ring 40 cantherefore be replaced with a pair of flat reflective bars spanning eachaperture, if desired. The integral ring 40 is preferred, however, sinceit facilitates manufacture and assembly of the mirror assembly 16'.

In the alternate embodiment of FIG. 4, the separate marker light source32 is eliminated. Instead, the internal light source (not shown) of aconventional stereo operating microscope 10' is employed. The receivingend of the fiber optic light guide 34 is re-routed through a loweropening in the housing 24. The light guide 34 terminates in a receivingend 42 having a small light collecting lens system located between thelower edge of the mirror assembly 16 (or 16') and the adjacent end ofthe lens 38 in the path of the light beam from the microscope. It hasbeen found that a sufficient portion of the light from the microscopesinternal source is present at the designated location of the receivingend 42 to provide light of sufficient intensity at the emitting end 36to form the marker point source. The receiving end 42 blocks only asmall portion of the light allowing the remainder to pass to the targetsite as intended. The structural requirements of the laser endoscope aresignificantly reduced by this unique configuration. Further details ofthis marker system are explained below in connection with FIGS. 10-12.

As shown in FIGS. 2 and 3, the mirror assembly 16 (or 16') is mounted ina gimbal assembly within the housing 24 having two orthogonal axes ofrotation which permit selective universal orientation of the assembly16. A pair of axles 44 and 46 are formed on opposite ends of the mirrorassembly 16 for rotation thereof about a central longitudinal axisrunning through the centers of both apertures in the plate 18. The axles44 and 46 are rotatably received in respective bearings 48 and 50 formedon opposite sides of a box-shaped outer gimbal 52. The upper and lowerends 52a and 52b of the outer gimbal 52 are open, or at leasttransparent, to allow passage of light to the microscope l0 andtransmission of the laser beam 27 to the work site 12. The mirrorassembly 16, rotatable within the outer gimbal 52, forms the innergimbal.

The outer gimbal 52 is mounted for rotation within the housing 24, asshown in FIG. 3. Annular neck portions 52c and 52d are formed on eitherside of the outer gimbal 52. The outer surface of the neck portions 52cand 52d serve as axles and are received in bearings 54 and 56,respectively, located in the housing 24 such that the open centerportion of neck 52d is aligned with the opening 26 in the housing 24 sothat the laser beam 27 can be directed toward the mirror assembly 16.The axis of rotation for the outer gimbal 52 may thus be thought of as aline connecting the respective centers of neck portions 520 and 52d.This rotational axis is perpendicular to the axis formed by axles 44 and46 for the mirror assembly 16, as can be seen by comparing FIGS. 2 and3.

The gimbal mounted mirror assembly 16 is designed to be mechanicallyoriented by manipulating a handle or joy stick 66, shown schematicallyin FIG. 2. The joy stick 66 is mounted for universal, pivotal movementabout a point 68 in a housing 70 adjoining the gimbal assembly housing24. The joy stick 66 is connected by a mechanical linkage 72 to themirror axle 44 so that pivotal movement of the joy stick 66 in a planeperpendicular to the plane of the paper in FIG. 2 causes proportionalrotation of the mirror assembly 16 on its axles 44 and 46 withoutchanging the orientation of the outer gimbal 52. The joy stick 66 isalso connected to the outer gimbal 40 through a mechanical linkage 74such that pivotal movement of the joy stick 66 in the plane of the papercauses rotation of the outer gimbal 52 about its axis of rotation, whichis perpendicular to the paper of FIG. 2 and is designated by point 75.Oblique movement of stick 66 in a direction having both parallel andperpendicular components resulting in corresponding proportionalrotation of both the mirror assembly 16 and the other gimbal 52 causinga complete reorientation of the mirror gimbal assembly with respect tothe microscope 10. The linkages 72 and 74 are designed to move theposition of the focal point of the reflected laser beam 27 approximatelyin proportion to and in the same sense or direction as movement of thestick 66. The object is to allow the positioning of the focused laserspot anywhere within a predetermined radius from the center of the fixedarea which comprises the microscopes field of view. As the orientationof the mirror assembly 16 is changed, the virtual marker image of thelight guide end 36 (FIG. 3) follows the changing location of the beamfocal point because the laser beam 27 and the marker light are reflectedfrom the same plane, although in opposite directions. It has been foundin a'device constructed according to the invention that the preferredlimits on the gimbal motion produced by the joy stick 66 permit thelaser beam to be steered to any desired location within i3 of themicroscopes central axis c. The diameter of the working area withinwhich the laser beam may be focused is therefore about one-tenth of theworking distance from the microscope objective to the work site 12.

An embodiment of the mechanical linkages between the joy stick 66 andthe gimbal assembly is illustrated in FIGS. 7, 8 and 9. The joy stick 66is connected to a pair of intersecting, orthogonal shafts 78 and 80rotatably mounted in the housing 70 by means of respective bearings 82and 84 (FIG. 8). The shaft 78 is parallel to the axis of rotation of theouter gimbal 52 and the shaft 80 is parallel to the nominal axis ofrotation for the mirror assembly 16. One end of the shaft 80 extendsthrough a vertical wall 70a inside housing 70 parallel to shaft 78. Thestick 66 is connected by means of a universal gimbal joint 76 to shafts78 and 80 such that movement of the stick 66 strictly perpendicular toone of the shafts 78, 80, rotates that shaft alone while the other shaftremains stationary.

An auxiliary shaft 85 spaced from the parallel to the shaft 80 ismounted for rotation above the shaft 78 in nominal alignment with theaxle 44 of the mirror assembly 16. Auxiliary shaft 85 is mounted at oneend in a bearing 86 formed in the outer wall of the housing 70. Theshaft 85 extends through another bearing 88 formed in the middle wall700. As shown in FIG. 9, a disc shaped cam 90 is eccentrically mountedon the end of the parallel shaft 80. An L-shaped crank 92 is rigidlyconnected at one end to the shaft 85. The other end of the crank 92 hasan adjustment screw 93 serving as a cam follower. Resilient means 94(shown only in FIG. 9) is connected between the crank 92 and the housing70 to urge the adjustment screw 93 into contact with the cam 90. The camand crank system connecting the shafts 80 and 85 causes proportionalrotation to be induced in the shaft 85 in response to rotation of theshaft 80.

The auxiliary shaft 85 has a hollow open portion formed by a large axialbore 95 which terminates within the shaft in a slotted bore 94 ofreduced diameter. A smaller shaft 101 is pivotally and slidably carriedwithin the shaft 85. The shafts 101 and 85 thus form a telescoping shaftassembly. The end of the smaller shaft 101 connected to the shaft 85terminates in a universal joint 103 slidably carried in the bore 97. Theshaft 101 can pivot about the center of the joint 103 out of true axialalignment with the shaft 95. The joint 103 has axle pins formed onopposite sides which fit into corresponding longitudinal slots orgrooves in the bore 97 so that the joint 103 and attached shaft 95 canmove axially with respect to the auxiliary shaft 85. The slidinguniversal connection between the shafts 85 and 101 permits axial andangular displacement of the shaft 101 while retaining the ability totransmit rotation or torque from the shaft 85 to the smaller shaft 101.The other end of the pivoting shaft 101 is coupled through openings inthe housing 70 and 24 to the axle 44 of the mirror assembly 16 by meansof another universal joint 105, which transmits rotation irrespective ofalignment between the pivoting shaft 101 and the mirror axle 44.Accordingly, rotation of the auxiliary shaft 85 produces precisely thesame amount of rotation of the mirror assembly 16' about itslongitudinal axis.

Another cam 107 is connected to the shaft 78. A crank 109 is rigidlyconnected to the side of the outer gimbal 52. The free end of the crank109 is fitted with an adjustment screw 110 which serves as a followerfor the cam 107. Resilient means 111 is connected between the crank 109and the housing to urge the adjustment screw 110 into contact with thesurface of the cam 107. Thus, rotation of the shaft 78 by movement ofthe stick 66 in the plane of the paper of FIG. 8 causes correspondingrotation of the outer gimbal 52 about its axis perpendicular to thepaper of FIG. 8 at point 75.

It should be carefully noted that rotation of the outer gimbal 52 aboutits axis out of its nominal position inherently causes angularmisalignment of the axle 44 and shaft and an increase in the distancebetween the universal joint and the auxiliary shaft 85. This is thereason why the connecting shaft 101 is both pivottaly and slidablywithin the shaft 85. The shaft 101 should be as long as possible tominimize its required angular displacement. The use of the hollow shaft85 in FIG. 7 accommodates a long shaft 101 while providing a compactarrangement for the cam and crank arm drive between parallel shafts 80and 85.

The details of the universal gimbal mounting 76 for the joy stick 66will now be described. The stick 66 is rigidly connected to a firstgimbal member 112 (FIGS. 7 and 8) in the shape of a flat vertical platewith bevelled sides having an oval aperture centered directly below thestick 66. An axle 114 aligned with the shaft 80 extends rotatablythrough a transverse bore in the shaft 78 from one side to the other ofthe oval aperture in the first gimbal member 112. The shape of theaperture in the member 112 provides clearance for pivoting the joy stick66 in a direction perpendicular to the paper of FIG. 8. The universaljoint 76 includes a U- shaped second gimbal member 116 having parallelupright sides rigidly connected to the respective intermediate ends ofthe shaft 80. An elongated slot 116a is formed in the base portion ofthe second gimbal member 116. A pin 118, axially aligned with the joystick 66 and rigidly connected to the bottom of the first gimbal member112, extends through the slot 116a.

Movement of the joy stick 66 in the plane of the paper of FIG. 8 rotatesthe shaft 78 causing rotation of the outer gimbal 52, but has no effecton the shaft 80 since the pin 118 is free to travel within the elongatedslot 116a between the parallel walls of the second gimbal member 1 16.On the other hand, perpendicular pivoting of the joy stick 66 has noeffect on the shaft 78 but results in rotation of the shaft 80, therebycausing mutual rotation of the auxiliary shaft 85, the pivoting shaft101 and finally the mirror assembly 16. When the joy stick 66 is movedobliquely, both shafts 78 and 80 are rotated simultaneously causing themirror assembly 16 to pivot about both of its gimbal axes at once.

The marker system of FIG. 4, in which the microscopes self-containedlight source is utilized, is shown in greater detail in FIGS. 10, 11 and12. It should be noted that, while the arrangement is similar, theapparatus is shown in a different orientation in FIG. 10. However, forthe sake of clarity, the same reference numbers as in FIG. 4 are used toidentify the corresponding components in FIG. 10.

For proper optical alignment of the marker system, both ends 36 and 42of the light guide 34 must be accurately positioned to achieve a brightpoint of light which appears to be perfectly coincident with the focalpoint of the laser beam 27. The light receiving ends 42 includes a smalllens system 120 for connecting light from the microscopes internalsource and concentrating it on the end of the fiber optic strand, whichmay be on the order of only 50 microns in diameter. The po sition andalignment of the end 42 is optimum when the maximum amount of light isconcentrated on the end of the fiber optic strand. A ball and socketassembly 122 (FIGS. and 11) allows universal adjustment of the receivingend 42. The light guide 34 passes through a central bore in a ball 124.The light guide 34 may be slidable in the ball 124 allowing axialadjustment or rigidly fixed thereto at the desired position. A pair ofapertures 126 and 128 (FIG. 11) are formed through the side wall of thehousing 24. A collar 130 is fitted into the aperture 126. One end 132 ofthe collar 131) is formed to serve as a portion of the bearing or socketfor the ball 124. An elongated clamp plate 134 is fixed at one end tothe inside of the housing 24 by a bolt 136 threaded into the housingwall on one side of the collar 130. The clamp plate 24 has an aperture138 aligned with the housing aperture 126. The wall of the aperture 138is bevelled on one side of the plate 134 to form the other portion ofthe socket for the ball 124. A plate 140 is secured to the outside ofthe housing 24 and has corresponding apertures aligned with apertures126 and 128 of the housing. A tightening screw 142 extends through theplate 140 and housing aperture 128 on the other side of the collar 130.The end portion of the screw 142 is threadably received through theother end of the clamp plate 134. The head of the screw 140 bearsagainst the plate 140. The ball 124 is thus retained in the socketformed by the collar 130 and clamp plate 134. By turning the screw 142,the plate 134 can be tightened down on the ball 124 to hold it in place.When the plate 134 is loosened slightly, the ball can be rotated. Thechannel through the outside plate 140, collar 130 and clamp plate 134through which the light guide 34 extends should be sufficient diameterto provide clearance for different orientations of the light guide.Although the bent end of the light guide 34 adjacent to the ball 124 isrigid, at least a portion of the light guide, between the ball 124 andthe point where the light guide reenters the housing (FIG. 10), must, ofcourse, be flexible to permit adjustment. For example, the portion ofthe flexible fiber optic strand extending through the ball 124 may becarried within a rigid sheath or pipe, and the portion of the strandexternal to the housing 24 may be carried within flexible tubing.

The light emitting end 36 of the light guide 34 is received in analignment assembly 144, shown in FIGS. 10 and 12, permitting adjustmentin three dimensions. The axial adjustment increases or decreases thedistance of the emitting end 36 from the lens assembly 38 for properfocus. Adjustments in a plane orthogonal to the axial direction permitcoinciding alignment of the virtual image of the emitting end 36 and thefocal point of the laser beam 27.

The light guide end 36 is coaxially and slidably received in a sleeve146 extending through an oversized aperture 148 formed in a cylindricalhousing 150 connected to the gimbal mirror housing 24 in coaxialalignment with the lens assembly 38. The sleeve 146 is axially held inthe aperture 148 by means of an annular lip 152 formed at one end of thesleeve and an annular fitting 154 with a set screw 156 slidablyreceiving the sleeve 146 on the other side of the housing 150. A setscrew 158 is thrcadably received in a transverse bore in the sleeve 146,external to the housing 150, to secure the light guide and end 36 at thedesired axial position.

A three point adjustment system is used to position the sleeve 146laterally within the oversized aperture 148. A pair of adjustment screws160 and 162 (FIG. 12) are carried in respective, threaded, radial boresformed in the end of the housing 150. The screws 160 and 162 areseparated angularly by about i.e., one-third of 360. The end of eachscrew 160, 162 contacts a respective indentation on the sleeve 146. Anannular groove 164 is formed coaxially in the sidewall of the oversizedaperture 148. The groove 164 lies approximately in the same plane as thescrews 160, 162, which therefore extend through the groove 164 tocontact the sleeve 146. A helical spring 166 is positioned in a portion(e.g. about 90) of the annular groove 164. The spring 166 contacts thesleeve 146 approximately at the mid-point along the springs length. Thepoint of contact should lie on the bisector of the angle between thescrew and 162 on the opposite side of the sleeve 146. The springsresistance to being bent from the straight condition (rather thanaxially compressed) is employed to urge or bias the sleeve into contactwith both screws 160 and 162. The diameter of the spring 166 should beless than the nominal radial distance between the outer surface of thesleeve 146 and the periphery of the groove 164. With this arrangementthe sleeve can be accurately positioned laterally by turning either one,or both, of the screws 160 and 162. For example, if the screw 160 alone(FIG. 12) is turned, the sleeve will pivot laterally in a small areabout the end of the screw 162.

The alignment assembly 144 for the light emitting end 36 is equallyapplicable to the embodiment illustrated in FIG. 3, in which a spearate,external light source 32 is employed.

With reference to the mechanical linkage for the joy stick 66, anydegree of demagnification of the movement of the mirror assembly 16'relative to the movement of the joy stick 66 can be accomplished byproper choice of the crank lengths (92, 109) and cam surfaces (90, 107).It has been found by experimentation that a proportionality constant ordemagnification of seven to one for both gimbal axes results in both ahigh degree of flexibility and control.

Those skilled in the art will recognize that other mechanical means ofconnecting shafts 80 and 78 to the mirror gimbal assembly are possible.For example, pulley systems or gears could be used. However, the crankand cam arrangement is preferred since it eliminates lost motion or playin the linkage and permits only oneway transmission of rotation.

Instead of using a pivoting shaft 101 with a universal coupling to theaxle 44 and a sliding universal connection to the auxiliary shaft 85, aflexible, torque transmitting cable, slidably carried in the shaft 85,can be directly connected to the axle 44. However, the arrangement usingrigid shafts is preferred since it reduces the play'between the axle 44and shaft 85.

In the above apparatus the marker light and laser 1 beam 27 are shownincident to the mirror assembly 16 at right angles to the microscopescentral axis 0. The mirror asssembly 16 (or 16) is therefore nominallyoriented at 45 with respect to the axis c. Other normal orientations forthe assembly 16 are feasible so long as ill the angles of incidence ofthe laser beam and marker light are changed accordingly. While themirror unit 16 has been described above in connection with the preferredgimbal assembly and joy stick control, it may be useful in certaincircumstances to eliminate the gimbal assembly, joy stick and mechanicallinkage and mount the assembly 16 rigidly at a prescribed angle withrespect to the axis c. This rigid mirror system would retain theadvantage of direct viewing of the work site through the mirrorapertures and the capability of loeating the laser beam focal point bymeans of the marker system. If the marker system is not needed, beamsplitters 20 and 22 or the ring 40 may also be eliminated.

The invention provides the capability of delivering laser energy at adistance while precisely locating the focused laser spot by means of amarker system prior to and during exposure and simultaneously viewingthe work site directly through a stereo operating microscope stationarywith respect to the work site. It is one of the central features of theinvention that the stereo laser endoscope accessory can be attached to aconventional stereo operating microscope without modifying themicroscope itself in any way. The conveniently mounted joy stickprovides sensitivity and naturalness of adjustment which allow thesurgeon to position the beam with confidence and precision.

It will be understood that various changes in the de tails, materials,steps and arrangements of parts which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is:

1. Microsurgical apparatus, comprising a stereo microscope for viewing awork site along a pair of converging stereo axes, a reflecting surfacepositioned at the light receiving end of said microscope between saidstereo axes and oriented to reflect a converging beam of energy towardsaid work site, and a plate mounted obliquely on the bisector of saidstereo axes and having a pair of spaced apertures located such that saidstereo axes pass through said apertures respectively, said reflectivesurface being formed between said apertures on a central portion of oneside of said plate facing said work site.

2. The apparatus of claim ll, wherein said stereo axes passsubstantially undeviated on either side of said refleeting surface.

3. The apparatus of claim 1, wherein said converging beam is an infraredlaser beam.

4. The apparatus of claim 1, further comprising reflecting meansconnected to said one side of said plate over said aperturesrespectively for reflecting light from the plane of said one side ofsaid plate along said stereo axes into said microscope.

5. The apparatus of claim 4, further comprising means for projecting adiverging beam of light at the other side of said plate such that saiddiverging beam is reflected from said apertures by said reflecting meansinto said microscope to form a virtual image indicative to the locationof the point of impact of said converging beam at said work site.

6. The apparatus of claim 5, further comprising a light source forilluminating said work site, said projecting means including lightguiding means having a light receiving end positioned to receive lightfrom said light source and having a light emitting end positioned toproject said diverging beam of light at said other side of said plate.

7. The apparatus of claim 6, wherein said light source is containedwithin said microscope.

8. The apparatus of claim 4, wherein said reflecting means over saidapertures includes a pair of beam splitting elements covering at least aportion of each said aperture respectively.

9. The apparatus of claim 4, wherein said reflecting means over saidapertures includes a fully reflective element covering only a portion ofeach said aperture.

10. The apparatus of claim 9, wherein said fully reflective element is aflat ring having one fully reflective side fixed to one side of saidplate and having portions extending over each said aperture.

ill. The apparatus of claim 10, wherein said flat ring has a taperedcross section whose width is greatest at said fully reflective side.

12. The apparatus of claim 1, wherein said reflecting surface is gimbalmounted.

13. The apparatus of claim 1, further comprising a gimbal assembly, saidreflecting surface being mounted in said gimbal assembly for rotationabout two orthogonal axes.

14. The apparatus of claim 13, further comprising a manual controlmember and means connecting said control member to said gimbal assemblyfor causing corresponding rotation of said reflecting surface in rcsponse to manipulation of said control member.

15. The apparatus of claim 1, further comprising an outer gimbal mountedfor rotation about an axis and having means for allowing theintroduction of said converging beam co-axially with respect to saidrotational axis and for allowing the transmission of said convergingbeam toward said work site after deflection by said reflecting surface,said plate being pivotally mounted in said outer gimbal for rotationabout an axis passing through both of said apertures perpendicular tosaid rotational axis of said outer gimbal.

16. The apparatus of claim 15, further comprising a manual controlelement and a mechanical linkage operatively connecting said controlelement to said plate and said outer gimbal for causing correspondingrotation of said plate and outer gimbal about their respectiverotational axes in response to manipulation of said control element.

17. The apparatus of claim 16, wherein said linkage includes a universalassembly connected to said control element, a pair of intersectingorthogonal rotatable shafts operatively connected to said universalassembly such that pivotal movement of said control element about thegeometric point of intersection of said orthogonal shafts is resolved bysaid universal assembly into rotation of each said shaft by an amountproportional to the corresponding orthogonal component of the movementof said control element, said pair of shafts each having a cam affixedthereto, a first arm having one end fixed to said outer gimbal and theother end urged into contact with said cam on one of said shafts, anauxiliary shaft parallel to the other of said shafts mounted forrotation, a second arm fixed at one end to said auxiliary shaft andhaving the other end urged into contact with said cam on said othershaft, and a rotational drive coupling connecting said auxiliary shaftwith said plate at said rotational axes of said plate.

18. The apparatus of claim 17, wherein said rotational drive couplingincludes a connecting element having one end coupled to said auxiliaryshaft and axially movable with respect thereto and having the other endcoupled to said plate.

19. The apparatus of claim 18, wherein said first and second reflectivemeans include coplanar reflective surfaces rigidly connected to eachother and mounted for rotation.

20. The apparatus of claim 17, wherein said rotational drive couplingincludes a connecting shaft having a first universal joint at one endcoupling said connecting shaft to said plate and having a seconduniversal joint at the other end, said auxiliary shaft having a hollowportion terminating in a slotted bore, said second universal joint beingslidably received in said slotted bore so that said auxiliary shafttransmits rotation through said connecting shaft to said plateregardless of misalignment of said rotational axis of said plate andsaid auxiliary shaft.

21. The apparatus of claim 17, wherein said first and second reflectivemeans are movably mounted together such that displacement of said firstreflective means causes corresponding displacement of said secondreflective means and said virtual image follows the location of saidfocal point.

22. Optical apparatus, comprising a microscope providing a field of viewfor observing a work site, reflecting means positioned between saidmicroscope and said work site, means for projecting a diverging beam ofvisible light at said reflecting means at an angle thereto such thatsaid diverging beam is reflected toward said microscope to provide avirtual image marking a location within said field of view, saidmicroscope being a binocular microscope having a pair of convergingstereo axes, and a plate mounted obliquely on the bisector of saidstereo axes and having a pair of spaced aperturcs located such that saidstereo axes pass through said apertures respectively, said reflectingmeans being formed between said apertures on a central portion of oneside of said plate facing said work site.

23. The optical apparatus of claim 22, wherein said reflecting meansincludes a beam splitting element positioned on one of said stereo axes.

24. The optical apparatus of claim 23, wherein said reflecting meansincludes another beam splitting element positioned on the other stereoaxis.

25. The optical apparatus of claim 22, wherein said reflecting meansincludes a flat ring having one fully reflective side obliquely facingsaid microscope and positioned such that opposite portions of said ringlie adjacent to said stereo axes respectively.

26. The optical apparatus of claim 25, further comprising a fullyreflective surface positioned between said stereo axes substantiallycoplanar with said fully reflective side of said ring for deflecting aconverging beam of energy toward said work site, said virtual imagebeing indicative of the location of the point of impact of saidconverging beam at said work site.

27. The optical apparatus of claim 22, further comprising a light sourcefor illuminating said work site, said projecting means including lightguiding measn having a light receiving end positioned to receive lightfrom said light source and having a light emitting end positioned toform a point source for projecting said diverging beam of light at saidreflecting means.

28. The optical apparatus of claim 27, wherein said microscope containssaid light source.

29. Microsurgical apparatus, comprising a microscope providing a fieldof view for observing a work site, a first reflecting surface positionedbetween said work site and the light receiving end of said microscopefor deflecting a beam of energy toward said work site such that thepoint of impact of said beam falls within said field of view, a secondreflecting surface positioned between said work site and said lightreceiving end of said microscope obliquely facing said microscope, meansfor projecting a diverging beam of light at said second reflectingsurface at an angle thereto such that said diverging beam is reflectedtoward said microscope to provide a virtual image indicative of thelocation of said point of impact, said microscope being a binocularmicroscope with a pair ofconverging stereo axes, said first reflectingsurface being positioned between said stereo axes and said secondreflecting surface being positioned on one of said stereo axes, and aplate mounted obliquely on the bisector of said stereo axes and having apair of spaced apertures located such that said stereo axes pass throughsaid apertures respectively, said first reflecting surface being formedbetween said apertures on a central portion of one side of said platefacing said work site.

30. The microsurgical apparatus of claim 29, wherein said microscope hasa self-contained light source for illuminating said work site and saidprojecting means includes light guiding means having a light receivingend positioned to receive light from said self-contained source of saidmicroscope and a light emitting end positioned to form a point sourcefor projecting said diverging beam toward said second reflectingsurface.

31. Microsurgical apparatus, comprising a stereo mi croscope providing anormally stationary field of view for observing a work site along a pairof converging stereo axes, a reflecting surface comprising a platemounted obliquely on the bisector of said stereo axes and having a pairof spaced apertures located such that said stereo axes pass through saidapertures respectively, said reflecting surface being formed betweensaid apertures on a central portion of one side of said plate facingsaid work site, said reflecting surface being positioned to reflect abeam of energy toward said work site such that the point of impact ofsaid beam falls within said field of view, and means for providinguniversal pivoting movement of said reflecting surface to change thelocation of said point of impact within said stationary field of view.

32. The apparatus of claim 31, wherein said means for providinguniversal movement includes a rotational mount providing said reflectingsurface with two orthogonal axes of rotation.

33. The apparatus of claim 32, wherein said means for providinguniversal movement further includes a pivotally mounted control elementand a linkage connecting said control element to said mount for causingcorresponding pivotal movement of said reflecting surface in response topivotal movement of said control element in any direction.

34. The apparatus of claim 33, wherein said linkages includes auniversal assembly connected to said control element, a pair ofintersecting othogonally mounted rotatable shafts operatively connectedat their junction to said universal assembly such that pivotal movementof said control element about the geometric point of intersecond armfixed at one end to said auxiliary shaft and having the other end urgedinto contact with said cam on said other shaft, and a rotational drivecoupling connected said auxiliary shaft with said reflecting surface forcausing rotation of said surface about the other orthogonal rotationalaxis.

35. The apparatus of claim 34, wherein said rotational coupling isaxially movable with respect to said auxiliary shaft.

UNITED STA'E ES PATENT OFFICE CERTIFICATE 0F CGRRECTION Patent No.3,796,220 Dated M rch 12, 1974 lnventofls) Herbert C. Bredemeier It iscertified that error appears in the above-identified patent and thatsaid- Letters Patent are hereby corrected as shown below:

' Column 1, line 21' "surgion's should read -surgeon's-.

Column 1, line 29 "surgion's" should read surgeon's.

Column 4, line 57, "splitter" should read -splitters--.

Column 7, line 24, "the" should read --and.

Column 9, line 21, "24" should read -34--.

Column 10, line 22, "screw" should read screws-.

Column ll, line 62 "to" should read -of-.

Column 13, line 63, "measn" should read -means--.

Column l6, 'line 4, "nected" should read -necting-.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JRo C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PC4050 (1069) uscoMM-oc eoa-le-pos U.5, GOVERNMENY PRlNTlNGOFFlCEi '99 -365'334'

1. Microsurgical apparatus, comprising a stereo microscope for viewing awork site along a pair of converging stereo axes, a reflecting surfacepositioned at the light receiving end of said microscope between saidstereo axes and oriented to reflect a converging beam of energy towardsaid work site, and a plate mounted obliquely on the bisector of saidstereo axes and having a pair of spaced apertures located such that saidstereo axes pass through said apertures respectively, said reflectivesurface being formed between said apertures on a central portion of oneside of said plate facing said work site.
 2. The apparatus of claim 1,wherein said stereo axes pass substantially undeviated on either side ofsaid reflecting surface.
 3. The apparatus of claim 1, wherein saidconverging beam is an infrared laser beam.
 4. The apparatus of claim 1,further comprising reflecting means connected to said one side of saidplate over said apertures respectively for reflecting light from theplane of said one side of said plate along said stereo axes into saidmicroscope.
 5. The apparatus of claim 4, further comprising means forprojecting a diverging beam of light at the other side of said platesuch that said diverging beam is reflected from said apertures by saidreflecting means into said microscope to form a virtual image indicativeto the location of the point of impact of said converging beam at saidwork site.
 6. The apparatus of claim 5, further comprising a lightsource for illuminating said work site, said projecting means includinglight guiding means having a light receiving end positioned to receivelight from said light source and having a light emitting end positionedto project said diverging beam of light at said other side of saidplate.
 7. The apparatus of claim 6, wherein said light source iscontained within said microscope.
 8. The apparatus of claim 4, whereinsaid reflecting means over said apertures includes a pair of beamsplitting elements covering at least a portion of each said aperturerespectively.
 9. The apparatus of claim 4, wherein said reflecting meansover said apertures includes a fully reflective element covering only aportion of each said aperture.
 10. The apparatus of claim 9, whereinsaid fully reflective element is a flat ring having one fully reflectiveside fixed to one side of said plate and having portions extending overeach said aperture.
 11. The apparatus of claim 10, wherein said flatring has a tapered cross section whose width is greatest at said fullyreflective side.
 12. The apparatus of claim 1, wherein said reflectingsurface is gimbal mounted.
 13. The apparatus of claim 1, furthercomprising a gimbal assembly, said reflecting surface being mounted insaid gimbal assembly for rotation about two orthogonal axes.
 14. Theapparatus of claim 13, further comprising a manual control member andmeans connecting said control member to said gimbal assembly for causingcorresponding rotation of said reflecting surface in response tomanipulation of said control member.
 15. The apparatus of claim 1,further comprising an outer gimbal mounted for rotation about an axisand having means for allowing the introduction of said converging beamco-axially with respect to said rotational axis and for allowing thetransmission of said converging beam toward said work site afterdeflection by said reflecting surface, said plate being pivotallymounted in said outer gimbal for rotation about an axis passing throughboth of said apertures perpendicular to said rotational axis of saidouter gimbal.
 16. The apparatus of claim 15, further comprising a manualcontrol element and a mechanical linkage operatively connecting saidcontrol element to said plate and said outer gimbal for causingcorresponding rotation of said plate and outer gimbal about theirrespective rotational axes in response to manipulation of said controlelement.
 17. The apparatus of claim 16, wherein said linkage includes auniversal assembly connected to said control element, a pair ofintersecting orthogonal rotatable shafts operatively connected to saiduniversal assembly such that pivotal movement of said control elementabout the geometric point of intersection of said orthogonal shafts isresolved by said universal assembly into rotation of each said shaft byan amount proportional to the corresponding orthogonal component of themovement of said control element, said pair of shafts each having a camaffixed thereto, a first arm having one end fixed to said outer gimbaland the other end urged into contact with said cam on one of saidshafts, an auxiliary shaft parallel to the other of said shafts mountedfor rotation, a second arm fixed at one end to said auxiliary shaft andhaving the other end urged into contact with said cam on said othershaft, and a rotational drive coupling connecting said auxiliary shaftwith said plate at said rotational axes of said plate.
 18. The apparatusof claim 17, wherein said rotational drive coupling includes aconnecting element having one end coupled to said auxiliary shaft andaxially movable with respect thereto and having the other end coupled tosaid plate.
 19. The apparatus of claim 18, wherein said first and secondreflective means include coplanar reflective surfaces rigidly connectedto each other and mounted for rotation.
 20. The apparatus of claim 17,wherein said rotational drive coupling includes a connecting shafthaving a first unIversal joint at one end coupling said connecting shaftto said plate and having a second universal joint at the other end, saidauxiliary shaft having a hollow portion terminating in a slotted bore,said second universal joint being slidably received in said slotted boreso that said auxiliary shaft transmits rotation through said connectingshaft to said plate regardless of misalignment of said rotational axisof said plate and said auxiliary shaft.
 21. The apparatus of claim 17,wherein said first and second reflective means are movably mountedtogether such that displacement of said first reflective means causescorresponding displacement of said second reflective means and saidvirtual image follows the location of said focal point.
 22. Opticalapparatus, comprising a microscope providing a field of view forobserving a work site, reflecting means positioned between saidmicroscope and said work site, means for projecting a diverging beam ofvisible light at said reflecting means at an angle thereto such thatsaid diverging beam is reflected toward said microscope to provide avirtual image marking a location within said field of view, saidmicroscope being a binocular microscope having a pair of convergingstereo axes, and a plate mounted obliquely on the bisector of saidstereo axes and having a pair of spaced apertures located such that saidstereo axes pass through said apertures respectively, said reflectingmeans being formed between said apertures on a central portion of oneside of said plate facing said work site.
 23. The optical apparatus ofclaim 22, wherein said reflecting means includes a beam splittingelement positioned on one of said stereo axes.
 24. The optical apparatusof claim 23, wherein said reflecting means includes another beamsplitting element positioned on the other stereo axis.
 25. The opticalapparatus of claim 22, wherein said reflecting means includes a flatring having one fully reflective side obliquely facing said microscopeand positioned such that opposite portions of said ring lie adjacent tosaid stereo axes respectively.
 26. The optical apparatus of claim 25,further comprising a fully reflective surface positioned between saidstereo axes substantially coplanar with said fully reflective side ofsaid ring for deflecting a converging beam of energy toward said worksite, said virtual image being indicative of the location of the pointof impact of said converging beam at said work site.
 27. The opticalapparatus of claim 22, further comprising a light source forilluminating said work site, said projecting means including lightguiding measn having a light receiving end positioned to receive lightfrom said light source and having a light emitting end positioned toform a point source for projecting said diverging beam of light at saidreflecting means.
 28. The optical apparatus of claim 27, wherein saidmicroscope contains said light source.
 29. Microsurgical apparatus,comprising a microscope providing a field of view for observing a worksite, a first reflecting surface positioned between said work site andthe light receiving end of said microscope for deflecting a beam ofenergy toward said work site such that the point of impact of said beamfalls within said field of view, a second reflecting surface positionedbetween said work site and said light receiving end of said microscopeobliquely facing said microscope, means for projecting a diverging beamof light at said second reflecting surface at an angle thereto such thatsaid diverging beam is reflected toward said microscope to provide avirtual image indicative of the location of said point of impact, saidmicroscope being a binocular microscope with a pair of converging stereoaxes, said first reflecting surface being positioned between said stereoaxes and said second reflecting surface being positioned on one of saidstereo axes, and a plate mounted obliquely on the bisector of saidstereo axes and having a pair of spaced apertures located such thaT saidstereo axes pass through said apertures respectively, said firstreflecting surface being formed between said apertures on a centralportion of one side of said plate facing said work site.
 30. Themicrosurgical apparatus of claim 29, wherein said microscope has aself-contained light source for illuminating said work site and saidprojecting means includes light guiding means having a light receivingend positioned to receive light from said self-contained source of saidmicroscope and a light emitting end positioned to form a point sourcefor projecting said diverging beam toward said second reflectingsurface.
 31. Microsurgical apparatus, comprising a stereo microscopeproviding a normally stationary field of view for observing a work sitealong a pair of converging stereo axes, a reflecting surface comprisinga plate mounted obliquely on the bisector of said stereo axes and havinga pair of spaced apertures located such that said stereo axes passthrough said apertures respectively, said reflecting surface beingformed between said apertures on a central portion of one side of saidplate facing said work site, said reflecting surface being positioned toreflect a beam of energy toward said work site such that the point ofimpact of said beam falls within said field of view, and means forproviding universal pivoting movement of said reflecting surface tochange the location of said point of impact within said stationary fieldof view.
 32. The apparatus of claim 31, wherein said means for providinguniversal movement includes a rotational mount providing said reflectingsurface with two orthogonal axes of rotation.
 33. The apparatus of claim32, wherein said means for providing universal movement further includesa pivotally mounted control element and a linkage connecting saidcontrol element to said mount for causing corresponding pivotal movementof said reflecting surface in response to pivotal movement of saidcontrol element in any direction.
 34. The apparatus of claim 33, whereinsaid linkages includes a universal assembly connected to said controlelement, a pair of intersecting othogonally mounted rotatable shaftsoperatively connected at their junction to said universal assembly suchthat pivotal movement of said control element about the geometric pointof intersection of said shafts is resolved by said universal assemblyinto rotation of each said shaft by an amount proportional to thecorresponding orthogonal component of the movement of said controlelement, said pair of shafts each having a cam affixed thereto, a firstarm having one end connected to cause rotation of said reflectingsurface about one of said orthogonal rotational axes and having theother end urged into contact with said cam on one of said shafts, anauxiliary shaft parallel to the other of said shafts mounted forrotation, a second arm fixed at one end to said auxiliary shaft andhaving the other end urged into contact with said cam on said othershaft, and a rotational drive coupling connected said auxiliary shaftwith said reflecting surface for causing rotation of said surface aboutthe other orthogonal rotational axis.
 35. The apparatus of claim 34,wherein said rotational coupling is axially movable with respect to saidauxiliary shaft.